Yoshimoto Ohta

Sesquiterpenes of nine european liverworts from the genera, Anastrepta, bazzania, jungermannia, lepidozia and Scapania

Abstract The essential oils of fourteen liverwort specimens from nine species of the Jungermanniales have been examined as to their sesquiterpenes. The barbatenes prove to be present in detectable amounts in all but one species. Bazzanene is frequently found with the barbatenes and new chemical evidence does not support the previously assigned structure but is consistent with a structure diastereomeric to trichodiene. This is consistent with a biogenetic rationale for the barbatene skeleton. Anasterptene, a novel crystalline tetracyclic hydrocarbon, has been found in numerous oils, and chemical degradation established a common skeleton with myliol. The samples of genus Scapania elaborate sesquiterpenes of the enantiomeric humulene-longifolene sequence. New members of this group found are (−)-β-longipinene, (−)-longipipanol, and (+)-γ-himachalene. The related germacrene series is represented by a cadinene, (−)-α-ylangene, and (−)-sativene. A series of cis-fused selinenes have also been found, which are more closely allied to the germacrene-sativene group than to typical trans-fused selinenes. One of these selinenes is shown to be the same as the material previously designated as sibirene. Scapania undulata also elaborates (+)-α- and β-chamigrene, and a number of novel hydrocarbons of still unknown structure.

Sesquiterpene constituents of two liverworts of genus diplophyllum: Novel eudesmanolides and cytotoxicity studies for enantiomeric methylene lactones

Abstract The steam distillates (or hexane extracts) of the liverworts Diplophyllum albicans (L.) Dum. and D. taxifolium (Wahl.) Dum. are largely a mixture of sesquiterpenes. Both species elaborate, among the hydrocarbons, mainly ent-α-selinene (8a) and ent-selina-4,11-diene (8b) together with anastreptene (1) and β-elemene (9). The major component of each essential oil was diplophyllin (10), a novel ent-eudesmanolide. The structure of diplophyllin was established by correlation with tetrahydro-isoalantolactone (17). In addition, the enantiomers of diplophyllin and diplophyllolide-A (16) were obtained on acid isomerization of isoalantolacetone (14a). Diplophyllin shows significantly greater activity against human epidermoid carcinoma (KB cell culture, ED50⋍ 8 μ g ml ) than its enantiomer: the first demonstration (to our knowledge) of optical selectivity for this type of cytotoxicity. Among the more polar constituents of D. albicans were 9α-acetoxy-diplophyllin, and several sesquiterpene alcohols including albicanol (22).

Sesquiterpenes of Barbilophozia species

Abstract Two isomeric olefins, α- and β-barbatene, apparently of a new tricyclic sesquiterpene skeleton (that of gymnomitrol), have been found in the liverworts Barbilophozia barbata, B. floerkei, B. lycopodioides, and B. attenuata. Additional components identified are alkanes, calamenene and α-alaskene. GLC suggests the presence of caryophyllene, longifolene, bazzanene and α-cedrene in minor amounts.

Induction of stress metabolite formation in suspension cultures of Vigna angularis

Abstract Three isoflavone glucosides were isolated from cell suspension cultures of red bean ( Vigna angularis ) treated with actinomycin D and identified as

Anastreptene, a commonly encountered sesquiterpene of liverworts (hepaticae)

Abstract Anastreptene ( 9b ), a tetracyclic mono-ene of the same skeleton as myliol ( 10 ) has been found as a common constituent of essential oils derived from liverworts. The relationship to myliol is established by spectral comparison between the hydroboration products and the related ketones from anstreptene and myliol degradation products. The additional degradative chemistry for anastreptene could not be rationalized based on the original myliol assignment ( 4 ), but accord with the recent revision based on X-ray crystallography and provide a confirmation of the stereochemical assignments for myliol and anastreptene.

Sesquiterpenes of thalloid liverworts of the genera Conocephalum, Lunularia, Metzgeria and Riccardia

Abstract Thalloid liverworts of orders Metzgeriales and Marchantiales elaborate essential oils distinguishable from those of the Jungermanniales by the absence of β-barbatene and anastreptene. Riccardia sinuata elaborates a novel tricyclic exomethylene sesquiterpene of as yet undetermined structure. Conocephalum conicum elaborates cadinene-type sesquiterpenes. β-Cadinene from the latter species is clearly enantiomeric to the same product from vascular plants.

The structure of isobarbatene, the stable tricyclic end-point of the bazzanene-barbatene sesquiterpenes

Abstract The barbatenes (e.g. 3) and a number of other sesquiterpenes afford a novel rearrangement product on treatment with CF3CO2H. This substance, designated isobarbatene, is shown to have structure 6, the result of a bicyclo-[3.2.1]→[2.2.2]→[3.2.1] rearrangement followed by an exo Me shift and deprotonation. The structure assignment is based on spectral and chiroptical data for olefin 6 and its degradation products 8,9 and 10.

Lunularic acid in cell suspension cultures of Marchantia polymorpha

Abstract Lunularic acid (LNA) was isolated from the cultured cells of the liverwort Marchantia polymorpha . Quantitative analysis by reverse phase HPLC showed that the content of LNA in the cells changed markedly during their growth, ranging from 1 to 7μg/mg dry wt. The accumulation of LNA was greatly enhanced by a deficiency of phosphate in the culture medium.

Prelunularic acid in liverworts

Abstract Prelunularic acid, the first example of an intermediate with a ‘pre-aromatic’ structure in the phenylpropanoid-polymalonate pathway, was isolated from suspension-cultured cells of Marchantia polymorpha . Its structure, including its absolute configuration, was assigned on the basis of spectral properties, direct conversion into lunularic acid, and CD measurements on the bis( p -dimethylaminobenzoate) of the methyl ester. Prelunularic acid was also detected in several liverworts of Marchantiales and Jungermanniales, and appears to be the immediate precursor of lunularic acid instead of the previously postulated hydrangenol or hydrangeic acid.

Rearrangement of zizaene-related sesquiterpenes

When set aside in formic acid, zizaene (I) and its presumed precursor (IV), yield a mixture of olefins [(V) and (VII)], epimeric at a centre separated from the olefinic bond by a quaternary centre.